Pretreatment of Lignocellulosic Biomass: Update on Biomass Refining CAFI Studies II

摘要

The Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI) was formed in 1999 as a multi-institutional effort to develop comparative information on cellulosic biomass pretreatment options. Major participants in the program are five university research programs that are leaders in the field of biomass pretreatment. Most recently, funding for this program is derived from both the United States Department of Agriculture, plus the United States Department of Energy through the National Renewable Energy Laboratory (NREL) and its contractor, Neoterics International. This paper will describe the logistical support and analysis efforts that NREL has provided to the consortium. NREL has provided the researchers with a common source of corn stover feedstock, a common source of enzyme preparations, training in analytical procedures, plus enzymatic hydrolysis and fermentation testing of pretreated corn stover provided by each researcher. The comparative enzymatic hydrolysis and fermentation testing is indicating performance differences among the pretreatment processes with respect to cellulose and hemicellulose conversion profiles and enzyme loading effects. The intent of this logistical support is to ensure that the experimental work is done on a consistent basis so that meaningful comparisons between the pretreatment options can be made. NREL has also provided process design, modeling and analysis resources. By developing an Aspen-based mass and energy balance model of each pretreatment type and integrating it into a complete biomass to ethanol model, down-stream effects have been identified that impact the economic viability of the processes. Additionally, NREL engineers fleshed out the available process data to include catalyst recovery, solid/liquid separation and neutralization steps necessary for the processes. Some generalized observations can be made from the model results: ? The economic projections show capital intensive facilities, yet cash operating costs are favorable compared to today's corn ethanol industry. ? Yield, of both five and six carbon sugar, is a strong driver of economics. ? Solids concentration in pretreatment will affect capital cost in almost all areas of the plant by causing higher flow rates throughout the process.